Sign conventions of concave and convex lens​

Explanation:

The New Cartesian Sign Convention of Concave and Convex Lens

According to the sign convention, a convex lens focal length is positive, whereas a concave lens focal length is negative. The incident light always moves from left to right because the object is always on the lens's left side.

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a straight line sloped

probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop